Snap-on presser foot shanks



Jan. 13, 1970 J. c. SECK 3,489,114

-SNAP-ON PRESSER FOOT SHANKS Filed Aug. 14, 1968 [NVENTOR John C. Seck ATTORNEY WITNESS United States Patent 3,489,114 SNAP-ON PRESSER FOOT SHANKS John C. Seck, Colonia, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 14, 1968, Ser. No. 752,663 Int. Cl. Db 29/12 US. Cl. 112-240 2 Claims ABSTRACT OF THE DISCLOSURE A sewing machine presser device is disclosed in which the sole plate may be readily detached and exchanged relatively to the shank. Each exchangeable sole plate is provided with a transverse pivot pin and the presser foot shank is formed with a pivot pin accommodating socket which by virtue of its shape and without the requirement of separate springs, detents, keepers or the like can releasably grasp the pivot pin of any selected sole plate.

Background of the invention This invention relates to sewing machine presser devices, and more particularly, to a presser device in which the sole plate may be exchanged readily without the need for manipulation of fastening devices requiring the use of tools.

The prior art includes a host of presser devices intended to provide for quick exchangeability of presser foot sole plates. In order to explain why the prior art devices have not provided the same solution to the problem as does the present invention, it is pointed out that a sewing machine presser foot is arranged closely adjacent to the stitching point in an area in which space requirements are critical. Quick exchangeable presser foot sole plate constructions heretofore known have included numerous articulated parts providing spring keepers, detents, and latch devices for holding the sole plate in place. In addition to being costly because of the number of different parts involved, the close tolerances required for proper cooperation, and the expense of assembly, these prior art devices not only usurp the critical space available in the vicinity of the stitching point, but also can catch and interfere with the sewing threads and the fibers of the work fabrics being stitched.

Summary of the invention The presser device of this invention exchangeably accommodates presser foot sole plates each carrying a plain transverse pivot pin. The presser device includes a depending integral shank blade formed with a pivot pin accommodating socket having a mouth sufiiciently constricted as to retain a sole plate pivot pin therein during ordinary sewing operations. From the socket a narrow elongate slot extends into the shank blade to provide the socket with sufiicient resiliency as to yield upon application of an abnormally high force so as to permit the transverse pivot pin of one sole plate to be taken out of the socket and that of a different sole plate to be replaced therein.

In the accompanying drawing illustrating a preferred form of this invention:

FIG. 1 represents a side elevational view of a fragment of a sewing machine illustrating the presser device of this invention,

FIG. 2 is a front elevation view of the presser device of this invention, and

FIG. 3 is a perspective view of the presser foot shank detached from a plurality of exchangable presser foot sole plates.

Referring to the drawings, FIG. 1 illustrates a fragment of a bracket arm 11 of a sewing machine frame including a bushing 12 secured in the bracket arm and a presser bar 13 endwise slidable in the bushing. The presser bar, as is conventional, may be biased downwardly by a spring (not shown) and furthermore, the presser bar may be raised at will by the machine operator by means of a presser lifting lever 14 carried on the bracket arm. Also endwise reciprocable in the bracket arm is a needle bar 15 carrying a needle 16 for the formation of stitches. The sewing machine frame includes a work supporting bed 17 beneath the bracket arm. Carried on the bed is a throat plate 18 which is formed with slots 19 through which a feed dog 20 of a conventional sewing machine feed mechanism is operative. Carried on the presser bar and urged downwardly against the throat plate and the feed dog is the presser device of this invention.

The presser device comprises a shank indicated generally as 21 adaptable for connection to the presser bar, and a sole plate indicated generally at 22 which may be exchangeably accommodated on the shank. In FIG. 3 two different presser foot sole plates 22 and 22' are illustrated, that indicated at 22 being of the type illustrated in FIGS. 1 and 2 which is adapted for use when sewing general purpose zigzag stitches; while the sole plate indicated at 22 is of a type adapted for sewing loose zigzag stitches over the edge of a fabric piece. In each case the sole plate is formed with upstanding ears 23 spaced apart a distance substantially equal to the thickness of the presser foot shank 21. Carried by the ears 22 and extending transversely therebetween on each of the sole plates is a cylindrical pivot pin 24.

The presser foot shank 21, which is preferably fabricated of a sheet metal stamping, is formed at the top with a U-shaped presser bar accommodating seat defined at one side by an outturned tab 25 and at the other side by outturned bifurcations 26. The presser foot shank is secured to the presser bar by means of a shouldered clamp screw 27 which passes between the bifurcations 26 and is threaded into the presser bar. Depending from the presser bar accommodating seat is a blade 28 in the bottom of which is formed a downwardly open socket 29 into which the cylindrical pivot pin 24 of a presser foot sole plate 22 may be accommodated.

The socket 29 is formed at the top as at 30 with a cylindrical conformation closely complemental to the cylindrical pivot pin 24 of the presser foot sole plates. The mouth of the socket 29 is constricted by protuberances 31 one at each side of the socket, the protuberances being spaced apart slightly less than the diameter of the pivot pin 24.

In order to control the resilience of the blade 28 of the presser foot shank so that the pivot pin of any selected presser foot sole plate may be maintained in the socket despite the usual forces acting on the presser device during sewing, but so that the pivot pin of any presser foot sole plate might be forced through the constricted mouth of the socket by application of a force of greater magnitude than that experienced during sewing for the purpose of exchanging sole plates. The presser foot shank plate 28 is formed with a narrow elongate slot 32. The slot 32 extends substantially lengthwise of the presser foot shank blade 28 and preferably joins the socket 29 at a position between the upper generally cylindrical portion 30 and the protuberances 31 defining the constricting mouth of the socket.

Because of the above described relationship between the slot 32 and the socket 29, the cylindrical portion 30 of the socket 29 which bears against the transverse pivot pin of a sole plate and provides a bearing therewith during use of the sewing machine will not be disrupted by the narrow slot, and yet the slot 32 can influence the resilience of the presser foot shank blade 28 so that when a force abnormally higher than that encountered during sewing is applied downwardly on the presser foot sole plate, the sole plate will be released from the presser foot shank and a different presser foot sole plate may be substituted therefor.

Best results will be obtained with the presser foot of this invention by selection of a type of steel for use in the fabrication of the presser foot shank which after forma tion of the socket 29 and the slot 32 may be subjected to heat treatment to provide for the requisite resilience without cracking in use.

As will be apparent in FIGS. 1 and 2, the device of this invention provides for exchange of sole plates Without requiring bulky space consuming constmction and without encumbering the area adjacent to the stitching point with complicated latching devices or assemblies of articulated parts which may snag the sewing threads or fibers of the work fabric being stitched.

Having set forth the nature of this invention what is claimed herein is:

1. A presser device for a sewing machine having a presser bar, said presser device including a shank detachably connectable to said presser bar and a sole plate, means for exchangeably securing said sole plate to said shank comprising a pair of spaced apart ears protruding upwardly from said sole plate, a cylindrical pivot pin carried in said spaced apart ears and extending trans versely therebetween, said shank being provided with a downwardly open pivot pin accommodating socket formed with a constricted mouth presenting an opening to said socket of smaller dimension than the diameter of said pivot pin, said shank being formed with an elongate slot narrower than the diameter of said pivot pin, said slot leading from said socket and extending substantially lengthwise of said shank.

2. A presser device as set forth in claim 1 in which said pivot pin accommodating socket in said shank is formed opposite the constricted mouth thereof with an upper portion of cylindrical conformation complemental to said pivot pin, and in which said elongate slot leads from a portion of said socket intermediate the upper cylindrical portion thereof and said constricted mouth.

References Cited UNITED STATES PATENTS 2,326,818 8/1943 Balzano 112-235 3,143,094 8/1964 Yamada ll2235 3,145,674 8/1964 Kurihara 112240 PATRICK D. LAWSON, Primary Examiner 

